| 摘要 |
PURPOSE:To diagnose the malfunction of a cooling water temperature switch accurately by deciding the contradiction of temperature on the basis of an electrical signal fed from a pressure switch which is subjected to the fluid pressure through the changeover function of a temperature sensitive valve disposed at same position with the cooling water temperature switch. CONSTITUTION:A thermowax type temperature sensitive valve 2 is fixed closely to a temperature switch 1 on the outer wall 30 of an internal combustion engine. The temperature sensitive valve 2 couples a port 6 to an atmospheric port 7 when the cooling water temperature is lower than a second predetermined level which is lower than a first predetermined level for closing the contact of the temperature switch 1 while couples the port 6 to an intake negative pressure port 8 when the cooling water temperature is higher than the second predetermined level. The port 7 is coupled to a pressure switch 13 and a controller 15 diagnoses the malfunction of the temperature switch 1 by combining the open/close conditions of the temperature switch 1 and the pressure switch 13. |
